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Laboratory for Atmospheric and Space Physics

SIM Releases Version 23

April 1, 2017

SIM Version 23 (V23) was introduced on May 2, 2017. Below are the release notes for V23, Level 3 data product.

SORCE SIM V23 employs the same correction methodology as employed in V22 but now includes a revision in the exposure time record bringing the exposure record up-to-date rather than extrapolating the exposure and increases the exposure time in before day 180 to account for non-physical trends in the earlier part of the mission.

  1. Processing code re-instates the daily calculation of SIM A and SIM B exposure time. This step required additional processing code changes because the SORCE planning page (employed prior to the DO-Op mode) does not necessarily reflect the actual executed experiments.
  2. As in V22 data, offset corrections are performed at the boundaries where spacecraft safe-hold events introduce offsets in the measured irradiance. Offset corrections are made by selecting time periods before and after the safe-hold events where the passages of solar active regions do not disturb the locally flat time series. The difference in the median irradiance for these two time ranges is added to the time series after the safe-hold event. This problem is exacerbated in the SIM data during the DO-Op mode since there is an ambiguity in closing the 225-day data gap in the extension of this record.

Users of SIM V23 should consult the V22 and V21 release notes for more information about the data correction methodology:

The successful resumption in the production of daily SIM data is reflected by continued agreement between the SIM A and SIM B channels in a time period spanning the 225-day time period. Examples of this are shown on the website release notes page (link above).

SIM V24 is in development and it will emphasize:

  1. Continued analysis of the effective solar exposure for the UV and the VIS photodiodes as the measurements proceed.
  2. The ESR data remains significantly noisier after the start of the power cycling due to temperature instabilities. These are attributed to either changes in the electrical characteristics of the ESR or a potential lag in the measured and actual temperatures of the ESR. This same observation is appropriate for the visible photodiode in the 850-950 nm range where some of the structure seen in the data reflect uncorrectable temperature instabilities.
  3. Additional analyses of the offset corrections.
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